1. Field of the Invention
The present invention relates to an ink jet printing apparatus, and in particular, to an ink jet printing apparatus including a dryer configured to dry ink on a print medium and a drying control method for the ink jet printing apparatus.
2. Description of the Related Art
Various dryers have been put to practical use which are configured to dry ink jet print media, photographic print paper, and the like with images printed thereon by image recording apparatuses such as ink jet printers or photographic photosensitive apparatuses. In these dryers, a temperature sensor is installed, and a fan is provided to blow air (hot air) heated by a heater against a print medium. A dryer control section, for example, controllably turns on and off the heater to maintain the temperature of the hot air at a predetermined value. The dryer control section thus dries the print medium being conveyed.
In a dryer that uses hot air, energy efficiency can be increased by making the dryer more properly closed and reducing heat leakage to the exterior. However, continuous drying may increase the humidity in the dryer to degrade drying capability. Moreover, if print media larger than standard ones are dried, the amount of moisture to be evaporated increases, thus making humidity likely to increase. This may result in an increase in outside air introduction amount. On the other hand, when a large amount of outside air is always introduced into the dryer so as to deal with large-sized print media, the heater consumes more power in order to maintain the temperature. This reduces the energy efficiency.
In a dryer disclosed in Japanese Patent Laid-Open No. 2002-268196, introduction of outside air into the dryer is avoided for a normal operation. When sheets of a size larger than a standard one are dried, outside air is introduced in order to increase air volume. This prevents the power consumption from being needlessly increased. Thus, energy saving is expected to be achieved.
If outside air the temperature of which is lower than that in the dryer is introduced, immediately after introduction of the outside air is started or the outside air introduction amount is increased, the temperature in the dryer decreases temporarily. For energy saving, the outside air introduction amount is preferably increased for print media larger than normal ones or print media with a large amount of moisture. However, in this case, immediately after the outside air introduction amount is increased, the temperature decreases by a larger amount. This may temporarily preclude sufficient drying.
Thus, the present invention has been developed in view of the above-described circumstances. An object of the present invention is to provide an ink jet printing apparatus and a drying control method for the ink jet printing apparatus in which when the outside air introduction amount is increased, degradation of the drying capability is suppressed.